This invention is concerned with anti-wheel lock-up systems for controlling skidding of a motor vehicle equipped with air brakes.
Systems of this general nature are known from U.S. Pat. Nos. 3,046,060 and 3,447,838, In the first of these, a mechanical unit for sensing and controlling an imminent wheel lock-up condition is located partly within the brake drum of a related wheel whereby a crowded condition with the usual required elements therein is created. In the second of these patents, the sensing unit is located externally of the wheel where it is subject to the elements of weather and other hazards.
A general objective of the present invention is to improve upon these known systems by providing one having various features and advantages resulting therefrom which are not present in these known system.
A feature of the system of the present invention is a miniture mechanical sensing unit or control device for controlling an imminent wheel lock-up condition in a vehicle, which unit is removably mounted in an open end of the axle tube supporting a related wheel, and which unit is protectively covered over by the hub cap of the wheel.
A very desirable advantage of this sensing unit arises from its location in the axle tube behind the hub cap, where it is guarded against attack by foreign particles or elements of the weather, is readily accessible for repairs or replacement, and does not occupy space usually required for an adequate accommodation of other elements.
A feature of the sensing unit is the manner in which it is operatively associated with the hub cap. This is of importance in that its arrangement does not require changes or modifications to be made in the brake drum of the released wheel, nor does it require components to be associated with the exterior of the wheel for its operation, as is required by the known devices mentioned.
Another feature of the present invention is a service air control module interconnecting a pair of sensing units with the braking mechanism of a pair of wheels for controlling the application to, and relief of service air from, the braking mechanisms when a wheel lock-up condition is imminent.
A desirable advantage of the module lies in its efficiency in controlling service air flow to the related braking mechanisms. It functions to maintain a minimum pressure of service air in the system in controlling an imminent wheel lock-up condition; it tends to lower system air pressure to match road conditions and aids in conserving air consumption. It further provides a plurality of cooperating valves in a single housing.
The foregoing, as well as other features, objectives, and advantages of this invention will appear more fully after considering the detailed description which follows in conjunction with the accompanying drawings wherein the invention is illustrated. It is to be expressly understood, however, that the drawings are for purposes of illustration and description, and accordingly they are not to be construed as defining the limits of the invention.